Dimethyl sulfide in the Amazon rain forest

Abstract

Surface-to-atmosphere emissions of dimethyl sulfide (DMS) may impact global climate through the formation of gaseous sulfuric acid, which can yield secondary sulfate aerosols and contribute to new particle formation. While oceans are generally considered the dominant sources of DMS, a shortage of ecosystem observations prevents an accurate analysis of terrestrial DMS sources. Using mass spectrometry, we quantified ambient DMS mixing ratios within and above a primary rainforest ecosystem in the central Amazon Basin in real-time (2010)(2011) and at high vertical resolution (2013)(2014). Elevated but highly variable DMS mixing ratios were observed within the canopy, showing clear evidence of a net ecosystem source to the atmosphere during both day and night in both the dry and wet seasons. Periods of high DMS mixing ratios lasting up to 8 h (up to 160 parts per trillion (ppt)) often occurred within the canopy and near the surface during many evenings and nights. Daytime gradients showed mixing ratios (up to 80 ppt) peaking near the top of the canopy as well as near the ground following a rain event. The spatial and temporal distribution of DMS suggests that ambient levels and their potential climatic impacts are dominated by local soil and plant emissions. A soil source was confirmed by measurements of DMS emission fluxes from Amazon soils as a function of temperature and soil moisture. Furthermore, light-and temperature-dependent DMS emissions were measured from seven tropical tree species. Our study has important implications for understanding terrestrial DMS sources and their role in coupled land-atmosphere climate feedbacks.

Atmospheric isoprene ozonolysis: impacts of stabilised Criegee intermediate reactions with SO<sub>2</sub>, H<sub>2</sub>O and dimethyl sulfide

“…Furthermore, Jardine et al (2015) recently showed that DMS mixing ratios within and above a primary Amazonian rainforest ecosystem can reach levels of up to 160 pptv, in canopy and above the surface, for periods of up to 8 h during the evening and into the night, with levels peaking at 80 pptv above canopy.…”

“…In a remote marine environment isoprene concentrations are probably an order of magnitude lower than this, and consequently [ISOP-SCI] would be calculated to be on the order of 4 × 10 1 molecules cm −3 . However, some regions will be impacted by both high isoprene and DMS concentrations, for example tropical islands, such as Borneo, which can have high isoprene concentrations and are strongly influenced by marine air masses (MacKenzie et al, 2011), as well as significant terrestrial sources from vegetation and soils in the Amazon, especially into the evening and at night (Jardine et al, 2015), when ozonolysis chemistry is at its most effective relative to photochemical OH chemistry. High sulfate composition of organic aerosols collected from the Borneo rainforests likely arises from the chemical processing of oceanic emissions of DMS and SO 2 (Hamilton et al, 2013).…”

“…DMS is a breakdown product of the plankton waste product dimethylsulfoniopropionate (DMSP). Jardine et al (2015) have also recently shown that vegetation and soils can be important terrestrial sources of DMS to the atmosphere in the Amazon Basin, during both the day and at night, and throughout the wet and dry seasons, with measurements of up to 160 pptv within the canopy and near the surface. The oxidation of DMS is a large natural source of SO 2 , and subsequently sulfate aerosol, to the atmosphere and is therefore an important source of new particle formation.…”

African volcanic emissions influencing atmospheric aerosol particles over the Amazon rain forest

“…Details about the ATTO site infrastructure, instrumentation and an overview of running measurements can be found elsewhere (Andreae et al, 2015). Figure 1 shows the ATTO site location and the place of the Nyamuragira volcano in the DRC located at 1.41° S, 29.2° E, 3058 m a.s.l.…”

“…In the Amazon rain forest, biogenic sulfate aerosol is sustained by oceanic DMS emission, and to a lesser degree by hydrogen sulfide (H 2 S), methanethiol (MeSH), and DMS emissions from soils and vegetation Jardine et al, 2015;Martin et al, 2010). Occasional anthropogenic sulfur injections have been attributed to open biomass burning and fossil fuel combustion emissions, either from Brazil or, via LRT, from Africa (Andreae et al, 1990;Talbot et al, 1988).…”